Epigenetics in Disease and Cancer

This area gathers the topics that connect epigenetic mechanisms — DNA methylation, histone modification, and chromatin remodelling — to human disease, with cancer as the central and best-characterised example. It treats epigenetic change as a heritable but potentially reversible layer of gene regulation whose disruption contributes to malignancy and to a growing list of developmental and acquired disorders.

Definition

Epigenetics in disease refers to the study of how alterations in gene expression that are not encoded in the DNA sequence itself — chiefly aberrant DNA methylation and histone modification — drive or contribute to pathological states, most prominently cancer.

Scope

The area orients the reader across cancer epigenetics, the silencing of tumour-suppressor genes through promoter CpG-island methylation, the therapeutic targeting of chromatin-modifying enzymes, and the rare constitutional disorders caused by mutations in the epigenetic machinery. It is a reference overview; the detailed essentials live in the individual topic entries beneath it.

Sub-topics

• Cancer Epigenetics
• CpG Island Methylation and Silencing
• Chromatin-Modifying Drugs and HDAC Inhibitors
• Rare Epigenetic Disorders

Core questions

• How do epigenetic alterations differ from genetic mutations in causing disease?
• Why does cancer show both global hypomethylation and focal promoter hypermethylation?
• Which disease-associated epigenetic changes are causal versus consequential?
• What makes the reversibility of epigenetic marks therapeutically attractive?

Key concepts

• Epigenetic dysregulation as a hallmark of cancer
• Reversibility of epigenetic marks
• Tumour-suppressor gene silencing
• Global hypomethylation versus focal hypermethylation
• Mutations in epigenetic-machinery genes
• Epigenetic biomarkers

Mechanisms

Disease-associated epigenetic change operates through the same machinery that maintains normal gene regulation. In cancer, the genome typically shows widespread loss of DNA methylation (hypomethylation), which can destabilise chromosomes and reactivate normally silent regions, alongside dense hypermethylation of CpG islands in the promoters of tumour-suppressor genes, which silences them without altering the underlying sequence. Histone-modification patterns and chromatin-remodelling complexes are likewise disturbed. Because these marks are written and erased by enzymes, the changes are in principle reversible, which distinguishes them from fixed genetic mutations and underpins epigenetic therapy.

Clinical relevance

Epigenetic alterations supply diagnostic and prognostic biomarkers and are the basis of an emerging class of chromatin-targeting therapies. This entry describes how epigenetic disruption relates to disease for educational orientation; it is not clinical guidance and does not direct diagnosis or treatment of any individual.

Epidemiology

Epigenetic alterations are detected across essentially all human cancers studied, and disrupted epigenetic regulation is increasingly recognised in developmental syndromes, metabolic and neurological disease. Precise population frequencies vary by disease and are addressed in the relevant topic entries rather than summarised here.

History

The link between epigenetics and disease was established through cancer research from the 1980s onward, when global hypomethylation and gene-specific hypermethylation were first documented in tumours. Successive reviews by Jones and Baylin, Esteller, and Feinberg synthesised these findings into a coherent picture in which epigenetic and genetic lesions cooperate in disease, and extended the framework beyond cancer to other human disorders.

Key figures

• Manel Esteller
• Stephen Baylin
• Peter A. Jones
• Andrew P. Feinberg

Seminal works

• jones-baylin-2007
• esteller-2008
• feinberg-2018

Frequently asked questions

How is an epigenetic change different from a genetic mutation?

A genetic mutation alters the DNA sequence, whereas an epigenetic change alters how genes are expressed — for example through DNA methylation or histone modification — without changing the sequence, and such changes are often potentially reversible.

Why is cancer the central example in this area?

Cancer is the disease in which epigenetic alterations have been most thoroughly mapped, showing both genome-wide hypomethylation and focal silencing of tumour-suppressor genes, which made it the model for understanding epigenetics in disease more broadly.